Event.observe(window, 'load', loadAccordions, false);

function loadAccordions() {
    var bottomAccordion = new accordion('vertical_container');

    var nestedVerticalAccordion = new accordion('vertical_nested_container', {
      classNames : {
            toggle : 'vertical_accordion_toggle',
            toggleActive : 'vertical_accordion_toggle_active',
            content : 'vertical_accordion_content'
        }
    });

    bottomAccordion.activate($$('#vertical_container .accordion_toggle')[0]);
}